Safety drivers for gun drills



Aug 30, 1960 E. D. oPPENHElMER SAFETY DRIVERS FOR GUN DRILLS Filed July13, 1956 m uw um f Q s .\J l.- H .l HUF HNHNNNIHMMH wulllh huw MMO/M mmw Q [Ln w, n@ mm WN mw n ml MN %N M am ww Q ,w M w QQ A @A E \|4 Q IIIUHHI ||||l| I |l|| IIIHIIMNWIII It l MW. mw uw @Q w ,f QQ mf L 'U S @n.Nulml mm NQ Q WQ@ SQQNN wm m @NQ 5m, QQ SUT NQ W N b Q Q s Q @www QQ QRN NN K R S .k n A. *LIM United States Patent O fiice SAFETY DRIVERS FonGUN DRlLLs Edgar D. Oppenheimer, Milford, Conn., assignor to EldoradoTool & Mfg. Corp., Milford, Conn., a corporation of 'Connecticut FiledJuly 13, 1956, Ser. No. 597,635

8 Claims. (Cl. 77--29) The present invention relates to driving devices,and it particularly relates to driving devices for a type of boring ordrilling mechanism known as a gun drill.

The present invention will be particularly directed to gun drills inwhich the relatively fragile drill or boring device is rotated, whereasthe work consisting of a piece of metal is held fixed. But it isunderstood that the present invention has a particular application tovertical and horizontal drilling or boring mechanisms, and it has quitewide application outside of this specific application.

The present invention will be particularly directed to the manner inwhich the fragile drill device is mounted and held during the drillingoperation and the manner in which the base of the drill is carried bythe spindle.

ln connection with gun drills, the work piece is frequently finishedbefore the drilling operation and represents a considerable expenditureof labor, and it is important that the drilling operation take placewith as high a rate as possible of finished perfect pieces which willpass inspection, without any substantial number of broken drills ordamaged work pieces, and without any likelihood that the work will beoperated on by a damaged drilling member during part or all of thedrilling operation. t

Another object of the present invention is to provide a safety systemwhich may provide automatic warning or automatic shut-od of the machine,which will give assurance of a higher percentage of perfect finishedwork pieces and a negligible number of damaged work pieces resultingfrom imperfections or breaking of the drills or other dificulties duringthe drilling operation.

Another object is to eliminate or decrease the possibility of breakageof the gun drill in the work due to operator or machine failure orresulting from undue wear or chipping of the cutting edge, all withoutsubstantially increasing the amount of labor involved or Vthe expense ofthe drilling operation.

A particular object of the present invention is to provide a safetyarrangement for gun drills of the character described in which therewill be maximum protection of the drill from both excessive torque andexcessive thrust, and in which, in case of development of eitherexcessive torque or excessive thrust, should either be provided -asignal or an automatic control should be actuated to stop the machine.

A further object of the present invention is to provide a safety devicefor gun drills of the character described, in which, in spite of thefact that the gun drill is rotated at a relatively high speed withliquid coolant being transmitted to the drill throughout the operation,such safety device will be operated in the presence of the coolant andnot be aiected by the high speed operation.

Still further objects and advantages will appear in the more detaileddescription set forth below, it being understood, however, that thismore detailed description is not given by way of limitation, sincevarious changes therein may be made by those skilled in the art Withoutdeparting from the scope and spirit of the present invention.

In accomplishing the above objects, it has been Jfound 2,950,636Patented Aug. 30, 1960 vide a friction drive as between the holder andthe carrier for the drill.

In one preferred form of the invention, the rotating spindle noseadapter is provided with a two-step plug oarn'er or driver, to which orupon which the drill shank is connected.

In the preferred form of the invention, the friction drive or contactand the torque is achieved by a wedging Contact or a contact over a Hator conical surface which will give the full necessary torque at the tipof the drill without consuming an excessive portion of the thrustexerted hydrostatically on the driver.

In la preferred construction, a friction plate is provided which isdesirably formed of hardened steel, which serves as friction contactmember and which is clamped in position by a threaded cap on therotating spindle nose adapter.

A small clearance is provided in the chuck so that part of the coolantwill always flush through the chuck arrangement and prevent any entry ofchips or dirt into the chuck arrangement, whereas the major portion, orsubstantially all of the liquid coolant, will pass through the drill andthen be returned through a groove or the exterior to the drill to the.end of the work piece, where it is discharged. If desired, smallsub-drivers or small sub-adapters may be provided to enable readychanging of 4drills Without changing the safety drivers or withoutopening the driver assemblies.

Where it is not possible to secure constant manual supervision of themachine, which would enable the operator to stop the machine uponexcessive load on the drill, a variety of simple mechanical, optical,electrical or audio safety arrangements may be provided.

In one preferred form of the invention a bell crank lever may operate inannular groove adjacent the safety driver and will be connected toactuate a limit switch.

=In another arrangement, a push rod may extend entirely through thespindle and may be connected to operate a switch at the pulley end ofthe spindle. Both devices may operate a warning buzzer, or shut 0E themachine automatically.

With the Iforegoing and other objects in view, the invention consists ofthe novel construction, combination and arrangement of parts ashereinafter more specifically described, and illustrated in theaccompanying drawings, wherein is shown an embodiment of the invention,but it is to be understood that changes, variations and modificationscan be resorted to which fall within the scope of the claims hereuntoappended.

In the drawings wherein like reference characters denote correspondingparts throughout the several views:

Fig. l is a longitudinal sectional view of one embodiment of the presentinvention, showing the spindle, spindle housing, together with thesafety driver and base portion of the drill.

Fig. 2 is an enlarged showing of the safety driver illustrated in smallscale at the right of Fig. l.

Fig. 3 is a side elevational View, partly in section, ofthe drill baseand plug, removed from the safety driver assembly, slightly modied toshow a sub-driver arrangement.

Fig. 4 is a side elevational view of the safety driver assembly of Fig.l modified to provide an alternative safety indicator arrangement.

Referring to Figs. l and 2, there are shown a spindle housing A, aspindle B, and an interior through push rod C for operating the limitswitch arrangement D.

Thespindle'B is driven by the pulley E, and it in turn drives the safetydriver arrangement F to which the present Adriver adapter G, which inturn receives in arecess the hardened inserti-I.. e Y .-The 'nsertineturnV has a ,recess receiving the spindle driver plug I which has therearwardlyextending, reduced .end portion K Vand the forwardly extendingportion'L which carries the gun drill M. The plug I is hydrostati-.cally forced against the hardened friction plate N, which is held inpositionby the internally threaded cap l. i Referring specifically toFig. l, the spindle housing A carries the ball bearing rings and 11,ywhich permit rotation of the spindle B, upon which is mounted thepulley E at itsleft end. j -The spindle B is boredV longitudinally at 12to receive Ythe shaft'or pusher rod C. VThis rod is a safety devicewhich will be described more fully.

` The pulley E is press-fitted, 'or otherwise held upon the reduceddiameter portion 13 of the spindle B by means of the threaded cap 14.-The spindle B is in turn clamped to the inner race of the ball bearing10 by the nut 15.V

At the other side, the shoulder 16 will be held against the inner raceofthe ball bearing 11. spindle has a flange-17 to which is attached theplate 18 of the spindle nose adapter G by the bolts 19.

The adapter Gf` is shouldered at 20 to receive the sleeve 21 which hasan inlet connection 22 for the coolant supply 23. This coolant mayconsist of a lubricant or cooling oil or other specially designedliquid.

The coolant may also be introduced through the hollow spindle B from therear of the machine, in which case the `radial feed 23 may bey omitted.

The liquid will flow into the peripheral groove 24 in the spindle noseadapter G and then ow through the radial passageways 25 into the centralrecess 26. The

adapter, as shown best in Fig. 2, has a central recess 27 in which islitted the hard insert 28 held in position by Vmeans of the set screw 29fitting in the groove or at 30 (see Fig. 2). f

The insert 28 has a longitudinal passage 45, which communicates with thethrough passage 26 to receive vthe coolant. i The rearwardlyextendingrmember K will closely fit in the passage with small clearance46. The pressure of the coolant will be exerted upon the face 47 as wellas on the shoulder 47a near the end of the reduced diameter portion 48.Y

thedrill M andreturn through the flute of such drill Q, bringing backany chips or waste material which may be discharged adjacent theadapter.

. 4 grooves 51 may be replaced by bores spaced Well inside of the outerperiphery of the plug J.

In the preferred form, the plug I has a main cylindrical section 55which has a reduced diameter section 56 with e. beveled forward section57 having the friction beveled face or frusto-conical gripping face 58.Less preferably, a at transverse contact face may be employed in lieu ofthe conical face.v

This 'contact face 458 acts upon'thre conical face 59 oftheA frictionplate N.

The friction plate N has an annular nose 60 lwhich ts into the periphery`of the recess 61, and also has a flange 62 which is'clamped between theface 63 and the hase 64 of the cap P.

'Ihe cap P has the openings 65 to receive a wrench to tighten it uponthe thread 66 and clamp the hardened friction plate in position. Theangle of` the driving contact 58--59 will afcorresponding Y Afect theamount Vof drivngtorque available, andthe ma- The end of the f YThecoolant Will flow through the central bore 49 into The leakage throughthe clearance 46 will permit flow of'oil'orcoolant into the recess orchamber 50 which receives the plugJ.V

Any leakage from the chamber 50 will pass through the grooves-51 in theplugl and through the space or annular passage 52 and then to theexterior, as indicated by the arrow 53, discharging and preventingentrance of any dirt or chips.

As a'result, although the chamber 50 will be lled with oil, suchpressure will be substantially atmospheric, due

to the release of anyexcess liquid through the grooves 51.

'The grooves 51 also balance the coolant pressure in the chamber 50 oneither side of plug I.

Sometimes at higher rotational speeds it is necessary to provideadditional venting for the chamber or space 50 and additional groovesmay be provided in the plug I or relief otherwise may be provided intothe chamber 50. yInsome instances, particularly athigh rotationalvelocities of the dn'll M, the centrifugal pressure of the liquid thatlls up the chamber 50 may press against the exterior of the face 54 toadd to the thrust applied to the face 47 to give extra pressure eifect.

Where it is Ydesired Yto use centrifugal pressure, the

terial selected for these contact faces `designed `so as to increase theVcoeflicient of friction. The angle should not be larger than 85fI andmay range from 0 to 85 with an optimum value between 45 and 60.

By referring to Figs. 1, 2 `and 3, it -will 'bc noted that the contactface 58 is carried upon a relatively thin disc. The thinness of the discwill give less weight to the plug, but `at the same time the disc mustbe suiciently rigid to carry the thrust and torque applied.

In order to enable rapid change of drills without opening up the driverassembly or changing the safety driver K-I-L,v ya sub-driver R may beutilized as shown in Fig. 3. In Fig. 3 there is shown a driver extension80 having an external groove 81 and 'a forwardly extending cup 82. Y

The cup 82 has a recess 83 to receive the extension 84 'of thesub-driver R. A threaded tip 85 is received in the tapped` socket `86.The head 87 will permit use of ya -wrench in installing and removing thedrill and sub-driver assembly.

The safety device C of Fig. 1 constitutes `a push rod having -a reducedforward diameter portion 100 and a reduced rearwardly extending portion1101. The rearward portion 101 is encircled by a spring 102 whichnormally biases the push rod C in the direction 103. The nut 104:1 will'act `as `a stop in the forward position. Y

The tip 104 will fbe normally spaced from a plunger member 105 ofa'limit switch D.

If the driver is forced inwardly, there will Ibe a con- .tactbetween theforwardly extending rod 106 `and the end 48 of the member K. This willresult in contact between the elements 104 rand 105 actuating the limitSwitch D to give a signal or to stopthe machine.

VThe slot'106b in the head 10651 permits'holding of the rod C when thenuts 104er is tightened up thereon.

The O-ring 107 will seal the member 100 in the passageway 108'in thespindle nose adapter G.

In the Yalternative safety arrangement shown in Fig. 4, the groove 81will carryV the nose 120 of the bell crank lever I121. The bell cranklever 121 is pivotally mounted at 122.

The arm 123 carries an `adjust-able contact rod 124 Whichis held in anypredetermined position by means of the nut 125. The rod 124 will contactthe recipro- -cating member 126 of the limitswitch 127 to stop the sureof the coolant most satisfactorily to give the necessary thrust asagainst a reduced diameter piston surface, while using a larger diameterconical thrust surface to achieve the desired torque.

The device `as shown will eliminate or decrease the possibility ofbreaking drill in the work due to operator or machine failure or becauseof undue wear or chipping of the cutting edge.

Even though the drill is relatively fragile, there will be less breakageand a greater production of perfect Work pieces and a minimum of scrap.

The safety driver device of the present application is particularlysuited to high production machines, and especially for fully automatic,-multi-spindle machines.

The safety device of the present application will protect the drill fromexcessive vtorque and excessive thrust, and not only will limit theseforces -but furthermore can signal the operator and/ or provide anautomatic control in case of overload.

The safety driver device of the present invention will accommodateitself to a wide variety of coolant pressures with varying drilldiameters, and will also accommodate a wide variety of feed rates andWork materials with varying conditions of wear at the cutting edge,

The hardened plate N may be made integral instead of separate from thecap P so that the plug will be pressed directly against the inside faceof the cup.

Instead of a separate cylindrical insert H to carry the rearwardextension K of the plug J, the element G may itself carry the extensionK, as well as the periphery of the plug l.

As many changes could be made in the above safety drivers for gundrills, and many widely different embodiments of this invention could bemade without department from the scope of the claims. It is intendedthat all matter contained `in the above description shall be interpretedas illustrative and not in a limiting sense.

Having now particularly described and ascertained the nature of theinvention, and what manner the same is to be performed, what is claimedis:

l. A drill having a rotating carrier with a chamber having a smalldiameter chamber and a large diameter chamber, a conduit to feed coolantunder pressure into said small chamber and a drill shank carrying plughaving a small diameter piston in said small chamber and a largediameter piston in said large chamber, said large piston and largechamber having cooperating annular frusto conical friction contact facesto cause said drill to rotate with said carrier, said faces being forcedtogether by the pressure of said coolant on said small piston in saidsmall chamber.

2. A driving arrangement for a boring and drilling mechanism comprisinga rotary carrier having a cylinderlike chamber system, a plug driverincluding a rearwardly extending plug guide member positioned in saidchamber system, a forwardly extending drill shank carried by saiddriver, said driver acting as a piston aud a conduit to supply coolantunder pressure to drive said driver against one end of said chamber andhold it there under friction upon rotation so that the driver andcarrier will turn together, the contacting friction faces of said driverand the end of the chamber being annular and extending around theinterior periphery of the chamber.

3. The arrangement of claim 2, said plug having a stepped peripheralportion with a conical contact face and said chamber also having aconforming conical contact surface.

4. The arrangement of claim 2, said plug and drill shank havingpasageways therethrough to pass the coolant through said chamber to thework being drilled and bored.

5. The arrangement of claim 2, a safety stop device actuated by movementof said plug through said chamber upon excessive load on said drillshank in the direction against coolant pressure.

6. The arrangement of claim 2, said driver having a small central faceon said guide member acted upon by said coolant pressure to cause thefriction contact.

7. The arrangement of claim 2, the chamber system having a small chamberto receive the guide member and large chamber to receive the driver withsmall clearance so as to limit leakage of coolant past the periphery ofthe guide member.

8. A drill arrangement having a separate housing, a rotatable spindle,bearings rotatably mounting said spindle in said separate housing, arotating spindle driver adapter carried by said rotatable spindle, arotatable drill driven by said spindle, said adapter having a large`diameter piston chamber at the side adjacent the drill and a smallerdiameter piston chamber communicating therewith at the side away fromthe drill, both having the same axis as the spindle, a spindle driverplug carrying said drill having a large diameter at piston disk mountedto reciprocate in said large piston chamber and -a small diameterelongated plug piston connected to the flat piston disk and extending inthe direction away from the drill and received in and mounted toreciprocate in said smaller piston chamber, a conduit rto feed coolantunder pressure into said chambers and to press the piston disk and plugpiston toward the ends of the chambers adjacent the drill, the peripheryof the interior of said large chamber at the drill side and theperiphery of flat piston disk at the drill side having contactingbevelled driving faces which cause -the disk and the drill to turn withthe spindle when said driving faces are pressed together by saidcoolantpressure.

References Cited in the le of this patent UNITED STATES PATENTS1,317,711 Landgra Oct. 7, 1919 1,760,310 Miller May 27, 1930 2,237,692Stewart Apr. 8, 1941 2,483,613 Benbow Oct. 4, 1949 2,562,170 BusemeyerJuly 31, 1951 FOREIGN PATENTS 586,385 Great Britain Mar. 17, 1947

